Shelf-stable foods prepared with microwave-assisted thermal sterilization may soon debut, provided the packaging riddle can be solved.
Commercial sterilization of food with microwave power inched closer to reality in August, when a pilot scale system arrived at Evansville, IN copacker AmeriQual. A second 22-ft. long R&D unit is expected to be delivered to another copacker, Cincinnati’s Wornick, by year’s end and foreshadows construction of an industrial-scale system.
The equipment is being built by Food Chain Safety, a Maple Valley, WA startup that licensed the technology from Washington State University. Known as MATS (microwave-assisted thermal sterilization), the technology was developed by Juming Tang, a WSU engineering professor, with funding from a coalition that included the US Army Natick Soldier Center, Kraft Foods, Hormel Foods and Masterfoods USA. Unlike the multi-mode signals used in home microwaves, a single-mode signal at 915 MHz bombards trays and pouches as they move through a tunnel in a shallow bed of water (see “Move over, retort,” Food Engineering, February 2010).
Both AmeriQual and Wornick are MRE suppliers to the military, using conventional retort to prepare field rations that can survive extreme temperatures and humidity. Improving the quality of those meals has been a long-running goal at Natick, and the military’s food scientists believe microwave sterilization represents a significant food-quality upgrade.
Two packaging companies were part of the WSU consortium, but neither firm is involved with the current project. Instead, Atlanta-based Printpack Inc. is filling the role of package developer. While microwaveable pouches and trays are well established for home use, surviving the sterilization process and maintaining oxygen-free integrity for 24 months is new territory.
Printpack recently scored a minor coup with a bag for Movie Theater Popcorn, a heat-and-serve popcorn in a microwave-safe bag from Popcorn, Indiana. “It took a few years to develop, but our packaging partner finally cracked the code,” says Jeff Dworzanski, marketing director for Englewood, NJ-based Popcorn, Indiana. “From a touch and look perspective, it’s the same as our other bags,” but the five-layer poly structure can withstand 30 seconds of microwave heating without leaching any chemicals.
The R&D units, named MATS-B, process about 10 items per batch in 10-12 minutes, according to Kevin Petersen, founder and chairman of Food Chain Safety. An order for the MATS-150 has been received, “and we’re in the process of building it now,” he reports. That machine, measuring about 85 ft. in length, will produce 150 units a minute. 
For more information:
Kevin Petersen, Food Chain Safety, 425-830-3750,